PREPARATION AND EVALUATION OF THE CHIRAL STATIONARY PHASES BASED ON N-4-(2,5,6-TRICHLORO-1,3-DICYANO)-PHENYL DERIVATIVES OF L-α-AMINO ACIDS

Abstract

Regioselective functionalization of 2,4,5,6-tetrachloro-1,3-dicyanobenzene (TCDCB) by nucleophilic substitution of the chlorine atom at C(4) for N-L-α-amino acid residue enables preparation of new chiral selectors (1-5). Their binding to aminopropyl silica gel afforded new brush-type chiral stationary phases (CSP-1–CSP-4). Chiral stationary phases CSP-5 and CSP-6 that comprise dipeptide units L-Ala-L-Pro and L-Ala-L-Ala, respectively, were obtained by the solid-state coupling of C(4)substituted derivatives of 2,5,6-trichloro-1,3-dicyanobenzenes 4 and 5 to γ-L-alanylaminopropyl silica gel. Best resolution for some of 23 test racemates was achieved with CSP-4 and CSP-6. This study reveals hydrogen bonding via a sterically exposed amide group and a π-π type interaction via an π-acid persubstituted benzene ring in these CSPs as the main contribution to chiral recognition.

ACKNOWLEDGMENTS

This work was supported by POLYtech S.c.r.l. (Area di Ricerca, Trieste, Italy) within the joint project on development of new enantioseparation processes. Valuable technical advice by Dr. Ahmed Aced, Iris Technologies Inc., is acknowledged.